1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus with a guide unit to guide a printing medium to a transfer unit, with a plurality of photosensitive mediums and waste developer receptacles integrated into a single unit, and with waste developer receptacles with different volumes to compensate for different rates of developer usage.
2. Description of the Related Art
Generally, an electrophotographic image forming apparatus such as a laser printer forms an electrostatic latent image on a photosensitive medium such as a photosensitive drum or a photosensitive belt. The laser printer then develops the latent image with a toner of a certain color, and transfers the developed image onto a print medium to produce the desired image.
Japanese Patent Publication No. H04-204871, which is titled “Color Image Forming Apparatus,” and which names Hiroshi Terada and Hidenori Kunishige as inventors, discloses an example of an image forming apparatus. The entire content of this publication is hereby incorporated by reference.
The image forming apparatus disclosed in Japanese Patent Publication No. H04-204871 comprises a plurality of rotatable photosensitive bodies. A plurality of developing means are disposed around the photosensitive bodies and develop images using toners of a plurality of different colors. The different color toner images are transferred to an intermediate transfer body, such as an endless belt, to form a full-color image. A transfer means transfers the color image on the intermediate transfer body to a transfer material (that is, a printing medium). A cleaning unit is included in the apparatus to clean any waste toner that remains on the photosensitive body.
Japanese Patent Publication No. H10-177286, which is titled “Image Forming Method and Apparatus Thereof,” and which names Nobuyuki Yanagawa as an inventor, discloses another example of an image forming apparatus. The entire content of this publication is hereby incorporated by reference.
The image forming apparatus disclosed in Japanese Patent Publication No. H10-177286 includes an intermediate transfer belt that receives single color toner images from photosensitive drums to form a full-color image. The full-color image formed on the intermediate transfer belt is transferred by a transfer means to a transfer material (that is, a print medium). The image forming apparatus comprises a first image forming unit I and a second image forming unit II which are spaced at a certain distance along the intermediate transfer belt. The first image forming unit comprises a developing means that develops an electrostatic latent image on a photosensitive drum with an A color toner and a C color toner. The second image forming unit comprises a developing means that develops an electrostatic latent image on a photosensitive drum with a B color toner and a D color toner (such as black).
Japanese Patent Publication No. 2001-75329, which is titled “Color Image Recording Apparatus,” and which names Noboru Otaki as an inventor, discloses yet another example of an image forming apparatus. The entire content of this publication is hereby incorporated by reference.
The color image recording apparatus disclosed in Japanese Patent Publication No. 2001-75329 is a LED (Light Emitting Diode) type printer and comprises a pair of printing tools A and B. The printing tools A and B are parallel to each other and spaced a certain distance away from each other in the same horizontal plane so that they form a color image on a printing medium. The printing tool A forms images with Y (yellow) toner and M (magenta) toner, and the printing tool B forms images with C (cyan) toner and K (black) toner. An intermediate transfer procedure is performed by an intermediate transfer belt. That is, the color image is transferred onto a printing medium by a transfer means contacting the intermediate transfer belt.
These types of image forming apparatuses require a guide structure for guiding the printing medium to the transfer unit to increase transfer efficiency. Conventional guide structures, however, have a complicated structure and are difficult to manufacture.
The image forming apparatuses described above also employ a cleaning unit for removing any waste developer remaining on the photosensitive drum or the intermediate transfer belt.
The cleaning unit generally comprises a cleaning blade that contacts the surface of the photosensitive drum or the intermediate transfer belt to scrape off any waste developer remaining on the surface of the photosensitive drum or the intermediate transfer belt, and a waste developer receptacle.
As shown in these published applications, the photosensitive drum may be used to provide two different colors. In this case, a plurality of cleaning units may be used with each photosensitive drum. Also, when a plurality of the photosensitive drums are used, the photosensitive drums need to be precisely spaced apart from each other so that the color images are properly registered when they are transferred to the intermediate transfer medium. With existing systems, maintaining appropriate spacing can be difficult, resulting in improper registration and poor image quality.
Furthermore, in an image forming apparatus that uses a plurality of photosensitive drums, the amount of waste developer on a photosensitive drum that forms an electrostatic latent image of a monochromatic image, such as black, is greater than that of other colors. Thus, it may be necessary to replace the waste receptacle more often than desired.
Accordingly, there is a continuing need for an improved image forming apparatus. In particular, there is a need for an image forming apparatus with an improved paper guiding structure, with an improved structure for maintaining registration, and with an improved waste toner receptacle.